1. Field of the Invention
The invention refers to a pump nozzle for Diesel engines, in which an injection pump element comprising a pump piston driven by a cam-shaft and a pump element bushing is combined with an injection nozzle to a unit to be associated to one motor cylinder each, wherein the pump piston is surrounded by a control sleeve being non-rotatable relative to the pump element bushing and being adjustable in direction of the axis of the pump piston in dependence on operating parameters of the motor for the purpose of varying the beginning of the injection and wherein the pump piston can be rotated relative to the control sleeve for the purpose of adjusting the supplied fuel amount. Such a control sleeve has, as a rule, a control edge located within a plane extending in normal relation to the pump axis and controlling the beginning of fuel injection. An obliquely extending control edge of the control sleeve or of the pump piston defines the end of injection and thus the injected amount of fuel in dependence on the rotated position of the pump piston relative to the control sleeve. By adjusting the height position of the control sleeve, the control edge defining the beginning of injection is earlier or later slid past the control bore of the piston, so that the beginning of supply by the injection pump is adjusted.
2. Description of the Prior Art
From DE-A1-31 43 073 there has become known a pump nozzle of the type in which the control sleeve is axially adjustable for the purpose of adjusting the beginning of injection. In this case, adjusting of the control sleeve is directly effected by means of a hydraulic piston. On account of adjusting the control sleeve directly by means of the hydraulic piston, the adjusting path of the control sleeve is equal the adjusting path of the hydraulic piston. On account of the adjusting path of the control sleeve being small, there are at disposal only small adjusting paths of the hydraulic piston for adjusting the control sleeve, so that such a control is not delicately sensitive and precise. In an embodiment according to the mentioned DE-A, the hydraulic piston is connected with the control sleeve via a linkage. Adjusting of the control sleeve becomes more inprecise on account of the play within the linkage. The control sleeve is immediately guided on the pump piston, so that wear is promoted between control sleeve and pump piston. The control piston is guided on the pump piston over a comparatively small guide length, so that there exists the risk for the control sleeve to become jammed on the pump piston, thereby increasing the wear of pump piston and control sleeve and further reducing the precision of control. In an other embodiment, the axially adjustable hydraulic piston surrounds the pump piston and is itself designed as the control sleeve. Also in this embodiment, the adjusting path of the hydraulic piston is thus equal the adjusting path of the control sleeve and therefore very small, and there are additionally required complicated sealings which equally detract from the precision and the sensitiveness of the control on account of the friction phenomenon.